Weird Idle?

[Zecrono]

Hello everyone, my 240 has been having a weird idle lately. When I approach a stop and throw it into neutral it dips into the 400s or 500s and shakes a little bit. I have my idle set to around 900rpms because it used to stall. It is not a vacuum leak because I blowed smoke through the brake booster and it came out fine. I unplugged both hoses on the brake booster and the one on the right popped off and let either in or out a burst of air. Maybe that has something to do with it? Thanks!

[The Inflicted]

Does the engine do this when cold, or only after it's warmed up a bit?

[Zecrono]

Does the engine do this when cold, or only after it's warmed up a bit?

Only after it's warmed up. Last night I was going about 50 down a straight back road and put it into neutral. My idle plummeted to 500 then jumped up to 1000 then back down, back and forth until I put it back into gear.

[The Inflicted]

In that case, the most likely cause of your idle fluctuations is the idle air controller valve, which may have become partially fouled and can't open properly.
Have you tried cleaning the valve?

iacv-aac-cleaning-and-testing-tutorial-t251133.html

[Zecrono]

In that case, the most likely cause of your idle fluctuations is the idle air controller valve, which may have become partially fouled and can't open properly.
Have you tried cleaning the valve?

iacv-aac-cleaning-and-testing-tutorial-t251133.html

I didn't actually take it out and clean it, I did exactly what you did and poured some injector cleaner down that one hose (thanks for that great writeup btw). Holy cow I drove it down the road and it looked like I made a new cloud. She definitely idles better with less frequent drops. The idle still fluctuates a few hundred rpms though. Not necessarily dropping but just moving around. Could it be my MAF sensor? The previous owner put a K&N oiled filter in it and that oil is on the inside casing (pipe?, wire?, idk what to call it).

[The Inflicted]

Not sure. In my case, cleaning the IACV was the last thing I tried and was what fixed everything. I had already tried a bunch of other stuff, like replacing the fuel filter, cleaning the MAF with MAF cleaner, cleaning the oxygen sensor, etc. etc.

[Zecrono]

Alright this is really making me angry. My car has been idling and starting weird for about a month now. When it is started cold it starts just fine, but if it is warm and I have let it sit for about 5 minuntes or more, it starts then the RPMs plummet to like 300 and the car shakes then it jumps back up to normal. When the engine is still warming up it tends to fluctuate a few hundred RPMs up and down. When it is warmed up and you accelerate, then throw it into neutral it idles at like 1k sometimes, then when I press the brakes to stop it drops to mearly 500rpms or lower and jumps back up after you come to a complete stop. I've had to up my idle quite a bit and when I set it to 750rpms with the TPS unplugged it constantly drops when coming to a stop to the point where it feels like it might stall at every stop.

Here is a video of it running with the MAF unplugged then plugged back in:


I tested the MAF and the voltages checked out (at least I know that its getting power and ground since it is a pain to test it connected). My TPS voltages checked out and is calibrated correctly. My injector impedance is: #4=5, #3=15, #2=17, #1=5. I couldn't find any vacuum leaks. Any other ideas? It also smells kind of rich, but that might have to do with the fact it still has the original cat I think. I can also hear a faint dripping sound coming from the intake side of the engine when I turn it off.

Its a bone stock KA just fyi

[Rogue One]

Hey Zecrono, you've already got an open thread on this problem so there's no need to start another one. I've merged the two threads.

[Zecrono]

Hey Zecrono, you've already got an open thread on this problem so there's no need to start another one. I've merged the two threads.

Wow I totally forgot I made this thread. Holy cow do I feel stupid lol. Thank you for that merge.